Wireless communications is one of the fastest growing industries. As with any industry faced with a large demand for products, wireless service providers are pressed not only to expand range of products but also to be more cost efficient. Unfortunately, the product to sell, which is, information transmission from one or more points to one or more other points, is limited by technology and regulations. Ubiquitous presence of wireless devices has stressed existing resources such as the fixed radio spectrum that is shared between typically all communication systems. Generally, the maximum range for wireless communications, is largely determined by amount of power that can be transmitted (and therefore received), and capacity is largely determined by amount of spectrum available. A fixed radio spectrum or bandwidth is statically allocated to the service providers by the Federal Communications Commission (FCC) and accordingly radio networks are statically designed based on traffic throughput.
A communication network such as a cellular telephone system is generally designed such that each cellular call is assigned a pair of frequencies, typically called an RF (radio frequency) channel, for duration of the call. The RF channel remains dedicated until termination of the conversation which is an expensive use of precious RF channel resources. Additionally, radio channels may be over allocated to certain sectors resulting in non-optimal use of available spectrum or spectrum holes where there may be no devices within an area, thereby consuming more bandwidth than necessary besides creating intra-network interference. Such wastage is not desirable in an environment where resources such as, available spectrum, are limited. Hence, service providers need to explore more efficient ways of using these limited resources.
In order to better utilize this resource, a wireless service provider generally divides a serviced area geographically into a number of cells and within these cells a single RF channel may be utilized by multiple consumers without interference if they are spaced apart beyond a certain distance. One methodology of assigning channels to cells is a fixed channel assignment (FCA) method wherein certain channels are permanently assigned to specific cells so that a given channel is assigned to two cells simultaneously only if they are spatially separated by the minimum distance. However, dynamic channel assignment (DCA) within cells wherein existing spectrum may be shared improves efficiency and results in better utilization of the limited resources.
More broadly there have been efforts referred to as “cognitive radio” that explore the feasibility of moving beyond tight assignments of ownership of spectrum and instead allow multiple players to make opportunistic usage of radio spectrum if the spectrum comes available in real-time.
More constrained notions allow a primary owner to cede secondary users usage of spectrum if communications activities by the secondary users do not interfere with the primary owner's applications. For example, a television operator may not have interest in using bandwidth within its allocated spectrum within a particular region, based on peripheral location of the region, and allow a secondary user to make use of that spectrum in that region should their be evidence that no disruptions will occur to television clients in that region (e.g., there are no people with televisions using the broadcast spectrum in that region).
In some applications, a primary user of bandwidth always has precedence but a secondary user can assume that the spectrum is available and use spectrum opportunistically should tests of usage (e.g., via listening to usage) e.g., monitoring two-way usage of the channel reveal that the channel is available to the secondary user.
In another variant a secondary user always has access to some expensive channel, but attempts to opportunistically gain access to a less expensive channel as it becomes available. In another scenario, a user has access to a channel with some set of properties such as bandwidth, but can opportunistically gain access to higher bandwidth channel that can be used to send higher fidelity transmissions.